[[WMG: Series/LifeAfterPeople takes place in the same universe as ''Series/{{Firefly}}''.]]
We all just left, explaining the lack of carnage.
* Also this theory can also be used/shared for the Creator/AnimalPlanet series TheFutureIsWild in where Humanity leaves the earth after a 2nd Ice Age.
* If we all just left, we left in a hurry, leaving everything running. Kind of like the whole planet sharing the fate of the ''Mary Celeste''...

[[WMG: Aliens did it.]]
The reason there are no humans left on Earth is that aliens abducted them all. IdiotPlot solved.

[[WMG: ''Life After People'' was filmed by time travelers.]]
It was listed as a documentary. But it is documenting events that have not happened yet. QED.
* Cue obligatory JustForFun/TimeLord reference.
** The History Channel is run by Time Lords? That's...[[{{FridgeBrilliance}} quite convenient actually.]]

[[WMG: ''Life After People'' was filmed by aliens]]
At times there are small camera effects that appear that someone (or something) is filming the show as if it were an actual live taping. And since the series at nauseum constantly insists that no humans survived the only logical conclusion is the entire show is filmed and produced by aliens who arrived shortly after '''[[TheEndOfTheWorldAsWeKnowIt The End]]''' perhaps to originally make a standard documentary about Humans. However after reaching the planet they discovered Humanity died out years ago from unknown causes and just decided to film the remains.

A couple of months later they give the footage to Network execs who give it the greenlight and it becomes one of the most successful series on "their" version of the HistoryChannel.

[[WMG: The people of Earth are gone because of the diabolical plans of Stanley from ''WesternAnimation/ATrollInCentralPark''.]]
He wanted to see a world that was 'absolutely green'. What we see at the end of his movie is the beginning of a Series/LifeAfterPeople.
* ........[[NightmareFuel oh god.]]

[[WMG: Humanity disappears in the year 2012]]
The Mayans were half right. The world survives, but humanity does not.
** Alternately, because the 2012 Mayan prophecy is actually supposed to be a prophecy of 'new beginnings' rather than the end of the world, it's actually a new beginning for the rest of the planet, not for humans. Kind of implies that HumansAreBastards though.
*** So very Jossed.

[[WMG: Humanity has been abducted by the Reapers]]
In an alternate history of the ''Franchise/MassEffect'' universe, the Reapers invade the galaxy before humanity discovers the Mass Relays. Humanity is destroyed alongside other sapient races, while the rest of planet Earth remains untouched.
** Then shouldn't the world be wartorn?

[[WMG: [[AIIsACrapshoot The machines have risen!]]]]
A sentient artificial intelligence (or group of AI's) has wiped out humanity, and is recording the decay of the civilization humanity left behind. Unfortunately the AI does not have sufficient capacity to spare every computer on the planet (or it deems non-AI machines as 'inferior' and not worthy of salvation).

[[WMG: [[WesternAnimation/InvaderZim The Irkens]] had something to do with it]]
Doesn't seem a bit dark and suspicious?

[[WMG: The population of Earth was exterminated by [[Series/DoctorWho Daleks]].]]

[[WMG: [[Series/StargateAtlantis The Wraith]] finally found the Earth.]]
And what a culling! This explains why people are just gone. The Wraith we burping and farting all the way back to Pegasus Galaxy.

[[WMG: Life After People is a prequel to Franchise/TheFutureIsWild]]
A world without humans,focusing on the changes of the environment and the animals on the future.Sounds familiar?

[[WMG: After humans go extinct, Earth becomes a WorldOfFunnyAnimals.]]
This theory is just like ''Disney/{{Zootopia}}''. Since humans never existed in that movie, the animals [[CivilizedAnimal evolve enough]] to use human technology in the aftermath.